High accuracy tape bearing surface length definition process for tape head fabrication

ABSTRACT

In one general embodiment, a method includes forming a slot on a tape bearing surface of at least a chip having a thin film layer with a plurality of transducers therein, the slot defining a skiving edge. A second operation is performed on the tape bearing surface of at least the chip for removing a portion of the chip positioned on an opposite side of the slot as the transducers.

BACKGROUND

The present invention relates to fabrication of magnetic heads, and moreparticularly, this invention relates to defining a tape bearing surfaceon a magnetic tape head.

Many modern electronic components are created by thin film waferprocessing. One category of component created by thin film processing isthe tape head. Another category is the disk head.

Most tape heads are currently built on wafers using thin film processes,similar to the wafers used for fabricating disk heads. However, theoperating efficiency of disk heads and tape heads are inherentlydifferent. Disk recording/reading is very efficient, as the disk mediais extremely flat and smooth, has a very thin magnetic layer, is in asealed environment, and the heads are constructed to function with aparticular media. Writing and reading tapes must address very differentchallenges. For example, the head should work with different tapebrands, which can have different physical and magnetic properties.Furthermore, most tape is composed of magnetic particles, which arecoated onto the tape surface. The resulting media can have variations incoating thickness and particle dispersion. This, coupled with spacingloss variations due to embedded wear particles and debris, requires thatmagnetic bits in tape be much larger than bits in disk media forachieving an acceptable signal-to-noise ratio.

Disk drive heads are designed to fly over smooth disk surfaces in acontrolled manner at speeds exceeding 30 to 40 meters per second. Bycontrast, tape stacking and other requirements limit tape driveoperating speeds to approximately 5 to 10 meters per second. Thus, toachieve data rates commensurate with disk drives, high performancelinear tape drives typically employ heads having multiple transducersthat operate simultaneously. For example, two transducers provide twicethe data rate of one transducer, and modern heads have 32 transducersfor each direction.

An important and continuing goal in the data storage industry is that ofincreasing the density of data stored on a medium. For tape storagesystems, that goal has led to increasing the track and linear bitdensity on recording tape, and decreasing the thickness of the magnetictape medium. However, the development of small footprint, higherperformance tape drive systems has created various problems in thedesign of a tape head assembly for use in such systems.

For example, tolerances decrease as feature size decreases. Moreover,smaller components tend to be more fragile than their largerpredecessors.

SUMMARY

A method according to one embodiment includes forming a slot on a tapebearing surface of at least a chip having a thin film layer with aplurality of transducers therein, the slot defining a skiving edge. Asecond operation is performed on the tape bearing surface of at leastthe chip for removing a portion of the chip positioned on an oppositeside of the slot as the transducers.

A method according to another embodiment includes coupling closures to asection of a thin film wafer having a plurality of rows of transducersformed on a substrate, the closures being coupled to the section on anopposite side of the transducers as the substrate. An end of the sectionis lapped for polishing the end of the section and the closure. A row issliced from the section, the row having the polished end. A slot isformed in the polished end. A tape bearing surface is defined betweenthe slot and portions of the transducers visibly exposed on the polishedend. A portion of the polished end located on an opposite side of theslot as the transducers is removed from the row or segment thereof.

Any of these embodiments may be implemented to fabricate a magnetic headusable with a magnetic data storage system such as a tape drive system,which may include the magnetic head, a drive mechanism for passing amagnetic medium (e.g., recording tape) over the magnetic head, and acontroller electrically coupled to the magnetic head.

Other aspects and embodiments of the present invention will becomeapparent from the following detailed description, which, when taken inconjunction with the drawings, illustrate by way of example theprinciples of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a tape head having closures.

FIG. 2 is a perspective view of a section of a thin film wafer accordingto one embodiment.

FIG. 3 is a perspective view of an array of closures.

FIG. 4 is a perspective view depicting coupling of the array of closuresto the section of wafer.

FIG. 5 is a perspective view of the array of closures coupled to thesection of wafer.

FIG. 6 is a perspective view of the closures coupled to the section ofwafer upon removing a top portion of the array of closures.

FIG. 7 is a perspective view of the section of wafer of FIG. 6 in aninverted position.

FIG. 8 is a perspective view of the section of wafer of FIG. 7 uponpolishing an end thereof.

FIG. 9 is a side view depicting cutting of a row from a section ofwafer.

FIG. 10 is a side view of a row cut from a wafer.

FIG. 11 is a perspective view of a row cut from a wafer after a back lapprocess to reduce a thickness thereof.

FIG. 12 is a perspective view of a chip cut from a row.

FIG. 13 is a perspective view of a U-beam with a chip coupled thereto,thereby forming a module.

FIG. 14 is a perspective view of a module upon defining a skiving edgethereon.

FIG. 15 is a perspective view of a module upon performing a secondgrinding operation.

FIG. 16 is a perspective view of a chip cut from a row.

FIG. 17 is a perspective view of a U-beam.

FIG. 18 is a perspective view of a U-beam with a chip coupled thereto,thereby forming a module.

FIG. 19 is a perspective view of a module upon forming of a skiving edgethereon.

FIG. 20 is a perspective view of a module upon performing a secondgrinding operation.

FIG. 21 is a perspective view of a U-beam according to one embodiment.

FIG. 22 is a perspective view of a U-beam with a chip coupled thereto,thereby forming a module.

FIG. 23 is a perspective view of a module upon forming of a skiving edgethereon.

DETAILED DESCRIPTION

The following description is made for the purpose of illustrating thegeneral principles of the present invention and is not meant to limitthe inventive concepts claimed herein. Further, particular featuresdescribed herein can be used in combination with other describedfeatures in each of the various possible combinations and permutations.

Unless otherwise specifically defined herein, all terms are to be giventheir broadest possible interpretation including meanings implied fromthe specification as well as meanings understood by those skilled in theart and/or as defined in dictionaries, treatises, etc.

It must also be noted that, as used in the specification and theappended claims, the singular forms “a,” “an” and “the” include pluralreferents unless otherwise specified.

The following description discloses several embodiments for producingtape heads having a precisely-positioned tape bearing surface edge.

In one general embodiment, a method includes forming a slot on a tapebearing surface of at least a chip having a thin film layer with aplurality of transducers therein, the slot defining a skiving edge. Asecond operation is performed on the tape bearing surface of at leastthe chip for removing a portion of the chip positioned on an oppositeside of the slot as the transducers.

In another general embodiment, a method includes coupling closures to asection of a thin film wafer having a plurality of rows of transducersformed on a substrate, the closures being coupled to the section on anopposite side of the transducers as the substrate. An end of the sectionis lapped for polishing the end of the section and the closure. A row issliced from the section, the row having the polished end. Opticaldetection of a reflective feature on the polished end is used todetermine a location for a slot, which is then formed in the polishedend at the determined location. A tape bearing surface is definedbetween the slot and portions of the transducers visibly exposed on thepolished end. A portion of the polished end located on an opposite sideof the slot as the transducers is removed from the row or segmentthereof,

In yet another general embodiment, an apparatus includes a substrate, athin film layer on the substrate having transducers therein, and aportion of a slot extending along the substrate, the portion of the slotdefining a skiving edge. A length of a tape bearing surface between thesubstrate and the skiving edge is in a range of about 7 to about 30microns.

One category of component created by thin film processing is the tapehead. FIG. 1 depicts one such tape head 100. The head 100 includes apair of head portions 102, each having a closure 104 that engages thetape 106 as it passes over the tape bearing surface of the head 100. Thetape bearing surfaces may angle upwardly (towards the tape) so the tapewraps both substrate and closure edges.

According to the preferred method for forming the head, a wafercontaining multiple “chips” each having read and/or write circuitry isformed by traditional thin film processing. The thin film wafer is cutinto rectangular sections, sometimes called quads. FIG. 2 illustrates asection 200 of a thin film wafer according to one embodiment. As shown,the section 200 includes a plurality of rows 202 of circuitry formed ina layer 204 of thin films formed on a substrate 206. The section 200will eventually be sliced and diced to form a head or chip. Thecircuitry may include, for example, read transducers, write transducers,servo transducers, electronic lapping guides, etc. Each row 202 cancontain multiple head images. Thus, while each row contains two headimages in this figure, rows built according to various embodiments mayhave more than two head images.

FIG. 3 shows an array 300 of closures 302 that will be bonded to asection 200 of the wafer. The closures 302 may be of conventionalconstruction. As shown, the closures 302 in this example extend from atop portion 304.

FIG. 4 illustrates how the array 300 is bonded to a section 200. Aconventional adhesive may be used to bond the array 300 to the section200.

FIG. 5 depicts the array 300 of closures 302 bonded to the section 200of wafer. The top portion 304 of the array 300 of closures 302 may beremoved prior to slicing the section 200 into rows 202. Portions of theclosures 302 themselves may be removed as well to define the length ofthe tape bearing surface of each closure 302. Grinding, lapping, and/orother subtractive process may be used.

FIG. 6 shows the closures 302 and section 200 with the top portion 304of the array of closures 302 removed. The portions of the closure 302remaining after processing support the tape as the tape passes over thehead to protect the delicate electronics in the head from wear.

FIG. 7 shows the section 200 of FIG. 6 inverted from the orientationshown in FIG. 6.

Referring to FIG. 8, the end 702 of the section 200 is lapped forsetting the approximate stripe height of the transducers. Conventionallapping techniques may be used.

Referring to FIG. 9, a row is then sliced from the section 200.Conventional cutting techniques may be used to slice the row from thesection 200 adjacent the transducers 1002. For example, a blade 1000 ofconventional construction may be used to cut through the section 200.

FIG. 10 depicts the row cut from the section 200. Various process stepsmay be performed on the row. For example, a back lapping step may beperformed on the substrate 206 to reduce its thickness, and/or to createa smooth bottom end for subsequent processing. FIG. 11 depicts the rowafter back lapping.

If the row includes multiple head images, the row may be cut into chips.Preferably, the rows are cut into individual thin film elements, orchips 1200, using conventional methods. See FIG. 12, which illustratesone chip 1200.

Each chip 1200 may be coupled to a beam such as a U-beam 1300, as shownin FIG. 13.

Additional processes may be performed, before or after the chip 1200 iscoupled to a beam. For example, the row or chip may be lapped again,using conventional techniques such as KISS lapping on a charged plate.Milling may be performed, e.g., for preparing the polished surface forapplication of a protective overcoat thereto. A conventional protectiveovercoat may be applied to the polished end.

A grinding process is performed in at least two steps. The firstgrinding operation is very shallow, and creates a slot 1404 that definesa tape bearing surface 1402 between an edge of the slot 1404 and thethin film layer 204. Where a portion of the circuitry of the thin filmlayer 204, exposed on the polished end, is used as the optical landmarkfor the slot positioning, the length of the tape bearing surface 1402between the slot 1404 and that portion of the circuitry may be veryaccurately defined.

Any conventional mechanism for forming the slot may be used. In apreferred embodiment, a conventional grinding wheel in a system withmachine vision may be used to create the slot at the proper location.

Being shallow and with the grinding wheel captive on both edges, thefirst grinding operation is precise and does not generate a significantcusp, where a cusp is a lip on the ground edge produced by compressivestresses during grinding. The cusp should be avoided as it tends tocreate non-uniform air leakage into the head-tape interface, resultingin unacceptable increase in spacing.

Subsequently, a portion of the chip 1200 located on an opposite side ofthe slot 1404 as the circuitry in the thin film layer 204 is removedusing a conventional technique such as grinding. FIG. 15 shows the chip1200 upon removal of the material. Preferably, the removal extends alongthe slot 1404, thereby allowing the remaining portion of the slot 1404to define the skiving edge of the tape bearing surface of the chip.Preferably, the second operation removes all remaining material in onepass.

Referring to FIG. 14, the slot 1404 may be located a distance D of lessthan about 30 microns, and preferably between about 10 and about 20microns, from the thin film layer 204. This distance D, in combinationwith a wrap angle of a tape relative to the skiving edge of the bearingsurface slot, is preferably short enough to induce tape tenting abovethe thin film layer 204 when a tape passes above the thin film layer204. Accordingly, D is preferably less than about 50 microns. In someembodiments, D may be in a range of about 7 microns to about 30 microns.Such tape tenting may prevent asperities and other defects on the tapefrom engaging the thin film layer 204 and causing damage thereto such assmearing of conductive material across the sensor, thereby creating ashort.

Two or more beams 1300 may eventually be coupled together to form ahead.

Preferably, the closures are angled upwardly into the tape bearingsurface (i.e., as they approach each other, preferably at an anglebetween 0.1 to 2 degrees, with respect to the horizontal line betweenthem. The angle of the closures may be used to create an air skivingeffect for close head-tape spacing and/or to create a tenting effect.

Preferably, the wrap angle between the two modules creates the desiredtenting over the read transducers.

As shown in FIG. 15, the chip 1200 is at least as wide as a tape forwhich the tape bearing surface is designed. However, other embodimentsare contemplated. For example, shorter chip may be fabricated, asdescribed immediately below.

According to various embodiments, the processes described herein may beused to form a partial span flat or contoured head “chip,” the chipbeing embeddable in a flat or contoured beam, such that the chip closureextends beyond the beam edges. For example, the rows may be cut intoindividual partial span heads, or chips 1600, using traditional methods.See FIG. 16, which illustrates a partial span flat profile chip 1600according to a preferred embodiment. If the chip is to be used in aLinear Tape Open (LTO) head, the preferred length of the chip in adirection perpendicular to the direction of tape travel thereover ispreferably less than about 7 to 8 mm, though larger or smaller sizes maybe created as well.

Similar processes as those described above with reference to FIGS. 2-13may be used to form the chip 1600, with the exception of the length ofchip cut from the section.

FIG. 17 illustrates a flat profile beam (carrier) 1700 according to oneembodiment. One skilled in the art will understand that many differentshapes of the beam can be used. For instance, the beam may be blockshaped, e.g., have a generally rectangular cross section when viewedfrom the tape bearing surface. The beam may also include rounded and/ortapered portions. For simplicity and ease of understanding, thefollowing description will be described with reference to a U-shapedbeam, or U-beam.

With continued reference to FIG. 17, the U-beam 1700 has a recess 1702extending into a tape bearing surface 1704 thereof. The U-beam ispreferably formed from a blank piece of wafer stock, which isinexpensive to fabricate, but is long enough to fully support the tape.If the U-beam is to be used in an LTO head, the preferred length of theU-beam in the same plane as, but in a direction perpendicular to, thedirection of tape travel thereover is preferably less than about 50 mm,and ideally less than about 25 mm, but may be longer. Before the chip isaffixed to the U-beam to form the module, the tape bearing surface onone of the U-beams may be lapped or polished to form a smooth tapebearing surface thereon.

As shown in FIG. 18, a chip 1600 is positioned in the recess of theU-beam such that the face 1710 of the substrate portion of the chip(which contains the device contact pads) is reasonably proximate to theadjacent face 1712 of the U-beam and coupled to the U-beam 1700 by anyconventional technique, such as via an adhesive, such that the chipclosure extends beyond the beam edges. This forms a module, which islater used to form a complete tape head. The geometry of the chip may bespecifically adapted to minimize closure protrusion, and therebyminimize tape deflections effects.

The tape bearing surfaces (of the chip and U-beam) should be as paralleland coplanar as possible because the tape will run across them. However,the tape bearing surfaces do not need to be perfectly coplanar, as thisdesign provides some tolerance for misalignment. Thus, the chip surfaceenvelope may deviate from the tape bearing surface of the U-beam byseveral micrometers. This tolerance relief greatly reduces fabricationcosts.

As shown in FIG. 19, the tape bearing surface of a U-beam 1700 and chip1600 can be processed, e.g., by grinding, to form a slot 1703 thatdefines a skiving edge 1706, hereby defining the distance of the tapebearing surface between the skiving edge 1706 and the thin film layer204. Such tape bearing surface may have dimensions similar to thosepresented above in the description of FIG. 14.

Referring to FIG. 20, a portion of the beam 1700 and chip 1600 locatedon an opposite side of the slot 1703 as the circuitry in the thin filmlayer 204 is removed using a conventional technique such as grinding.FIG. 20 shows the beam 1700 and chip 1600 upon removal of the material.Preferably, the removal extends along the skiving edge 1706 defined bythe slot 1703. The second grinding operation may remove all remainingmaterial in one pass.

Two beams 1700 can be coupled together to form a head with spacingbetween the central portions of the beams, such as a head of the typeshown in FIG. 1. Preferably skiving edges are formed on both modules toenable bi-directional reading and writing. In addition, the inside edges1705 may be made sharp so that these will also skive air. Alternatively,the inside edges 1705 may be rounded if desired.

Preferably, the closures are angled upwardly into the tape bearingsurface (i.e., as they approach each other, preferably at an anglebetween 0.1 to 2 degrees, with respect to the horizontal line betweenthem. The angle of the closures may be used to create an air skivingeffect for close head-tape spacing and/or to create a tenting effect.

Preferably, the wrap angle between the two modules creates the desiredtenting over the read transducers.

All of the read and/or write elements in the head are preferablypositioned in the chips. Note that each chip can have multiple read andwrite elements, such as interleaved read/write elements. Alternatively,one chip can have all write elements and the other chip can have allread elements. Other combinations are also possible. In this way, aread/write head can be formed.

FIGS. 21-23 illustrate an alternate embodiment having components similarto those of FIGS. 16-20, and accordingly have common numberingtherewith. As shown in FIG. 21, the beam 1700 has a rear skiving edge1706 already formed thereon. In FIG. 22, the chip 1600 is coupled to thebeam 1700. FIG. 23 shows the module after a portion of the chip 1600behind the bearing surface slot is removed by a multi-step grindingprocess.

The heads created by the processes described herein can be used inmagnetic recording heads for any type of magnetic media, including butnot limited to disk media, magnetic tape, etc.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, and notlimitation. For example, the structures and methodologies presentedherein are generic in their application to all types of thin filmdevices. Thus, the breadth and scope of a preferred embodiment shouldnot be limited by any of the above-described exemplary embodiments, butshould be defined only in accordance with the following claims and theirequivalents.

What is claimed is:
 1. A method, comprising: forming a slot on a tapebearing surface of at least a chip having a thin film layer with aplurality of transducers therein, the slot defining a skiving edge; andperforming a second operation on the tape bearing surface of at leastthe chip for removing a portion of the slot and a portion of the chippositioned on an opposite side of the slot as the transducers to a depthlower than the slot, wherein a portion of the slot remaining after thesecond operation forms a step positioned between the tape bearingsurface of at least the chip and a tape-facing surface defined by thesecond operation.
 2. The method as recited in claim 1, comprising:lapping an end of a section of a thin film wafer for polishing the endof the section, the section having a plurality of rows of thetransducers formed on a substrate; slicing a row from the section, therow having the polished end; and cutting the chip from the row, whereina length of the tape bearing surface is in a range of about 7 to about30 microns.
 3. The method as recited in claim 2, comprising couplingclosures to the section on an opposite side of the transducers as thesubstrate.
 4. The method as recited in claim 1, comprising using opticaldetection of a reflective feature in the tape bearing surface todetermine a location for the slot.
 5. The method as recited in claim 1,wherein a depth of the portion of the slot from a plane extending alongthe tape bearing surface is less than a difference of the depth of thetape-facing surface defined by the second operation minus the depth ofthe slot.
 6. The method as recited in claim 1, wherein the chip isinserted in a recess of a beam, wherein the slot is created in only thechip.
 7. The method as recited in claim 1, wherein the chip is insertedin a recess of a beam, wherein the slot is created in both the chip andthe beam.
 8. The method as recited in claim 7, wherein the secondoperation removes, from both the chip and the beam, a respective portionthereof on an opposite side of the slot as the transducers.
 9. Themethod as recited in claim 1, comprising adding a protective coating toat least the chip prior to forming the slot.
 10. The method as recitedin claim 1, comprising: lapping an end of a section of a thin film waferfor polishing the end of the section, the section having a plurality ofrows of the transducers formed on a substrate; slicing a row from thesection, the row having the polished end; and cutting the chip from therow.
 11. The method as recited in claim 10, comprising coupling closuresto the section on an opposite side of the transducers as the substrate.12. The method as recited in claim 10, comprising inserting the chip ina recess of a beam.
 13. A method, comprising: coupling closures to asection of a thin film wafer having a plurality of transducers formed ona substrate, the closures being coupled to the section on an oppositeside of the transducers as the substrate; lapping an end of the sectionfor polishing the end of the section and the closure; slicing a row fromthe section, the row having the polished end; forming a U-shaped slot inthe polished end, a tape bearing surface being defined between the slotand portions of the transducers visibly exposed on the polished end; andremoving, from the row or segment thereof, a portion of the polished endlocated on an opposite side of the slot as the transducers to a greaterdepth than a depth of the slot relative to a plane extending along thetape bearing surface.
 14. The method as recited in claim 13, comprisingcoupling at least a portion of the row to a beam, wherein the slotdefines a skiving edge of the tape bearing surface.
 15. The method asrecited in claim 14, wherein the portion of the row is at least as wideas a tape for which the tape bearing surface is designed.
 16. The methodas recited in claim 13, wherein the depth of the slot from the plane isless than a difference of the depth of the removing from the plane minusthe depth of the slot from the plane.
 17. The method as recited in claim13, wherein the slot defines a skiving edge of the tape bearing surface,wherein a portion of the slot remaining after the removing forms a steppositioned between the tape bearing surface and a tape-facing surfacedefined by the removing.
 18. The method as recited in claim 13,comprising cutting a chip from the row.
 19. The method as recited inclaim 13, comprising using optical detection of a reflective feature inthe tape bearing surface to determine a location for the slot.
 20. Themethod as recited in claim 13, comprising adding a protective coating tothe polished end prior to forming the slot.